Isolation between nearby circuit elements has been an object of intense investigation in the integrated circuit development field. Initially, p-n junctions were used to isolate adjacent elements, and more recently local oxidation techniques have been used to achieve lateral isolation between adjacent circuit elements. While these techniques have been useful, a practical means of completely surrounding a circuit element with an insulating layer of silicon dioxide has been sought to provide total isolation.
Traditional dielectric isolation technology requires critical mechanical polishing. Since the circuit density is low and the cost is high, this technology has been limited to specialized applications, such as radiation hardened integrated circuits. Silicon on sapphire has also been extensively developed, but the high substrate cost and limited device quality has restricted its application. More recently, melting and recrystallization of silicon films deposited on insulating layers has been a topic of major investigation. However, severe temperature gradients experienced during the recrystallization are a major limitation.